Path tracing solutions record the path within the live customer traffic. Examples of such solutions include In-band/In-situ Operations, Administration, and Maintenance (IOAM) or In-Network Telemetry (INT). These solutions use space in a packet which is directly proportional to the number of hops the packet travels. Examples of data stored within the packet include an identifier, timestamp, interfaces visited, queue depth etc., for each node the packet traverses.
For large networks with a large amount of nodes and/or long paths, this approach can result in a large amount of metadata that is required to be carried in the packet. The schemes which insert unique metadata on a per-hop basis suffer from implementation challenges. They either require changes to the size of the packet at every hop (which gives rise to Path Maximum Transmission Unit (PMTU) issues) or they require write operations into the packet at varying locations within the packet. In other words, a pointer is read from the packet and then data is dropped into the location the pointer indicates. This is not easy to implement in hardware.